The present invention relates to filter cigarettes. More particularly, the present invention relates to filter cigarettes which are adjustable to provide wide range of air dilution and/or resistance-to-draw (hereinafter "RTD") values.
Various mechanisms have been disclosed in heretofore issued patents which provide for adjustment of the air dilution value of a filter cigarette, but these mechanisms are not without certain disadvantages. While many complicated mechanisms have been disclosed, the simpler mechanisms generally involve making one or more openings through a substantially air-impermeable filter plug wrap and the overlying, substantially air-impermeable tipping paper and one or more corresponding openings in a sleeve which is placed over the tipping paper and which is then either rotated or moved axially to select the degree to which the two sets of openings are in registry. In another embodiment found in the art, the filter is not glued to the tipping paper and thus may be moved axially within the cylinder formed by the tipping paper. Openings are made in the filter plug wrap and corresponding openings are made in the tipping paper. The air dilution value is adjusted by axially moving the filter plug within the tipping paper to adjust the degree to which the two sets of openings are in registry.
Among the problems associated with such mechanisms are that the sleeve or filter plug may be removed from the cigarette by the smoker and not readily replaced, and that when dilution is desired, thus requiring some degree of registry between the two sets of openings, this registry may be inadvertently destroyed by a slight axial movement of the sleeve or plug. Accordingly, the dilution, once set by the smoker, is not insured of any degree of consistency. Yet another problem associated with a number of these prior devices is that they have not been readily adaptable to a high rate of production on cigarette making machinery of conventional design.
Accordingly, it is an object of the present invention to provide a cigarette which can be readily manufactured on conventional cigarette making equipment and that is adjustable to vary the ratio of air to smoke delivered to the mouth of the smoker.